Mi foto
Nombre: K.
Ubicación: Tuvalu

Pensé que no tenía origen, que simplemente era una letra que soñaba ser borboleta; tres líneas cruzadas que se asombraban con sus encuentros y desencuentros; pensé que era alguien a quien le aterrorizaba el aterrizaje y prefería usar las palabras para asirse a la tierra. Ahora sé que vengo de los jázaros y que los sueños (tanto dormida como despierta) son lo mio. Algunos (creen que) me (llaman) gusta el (ser) Bella Durmiente. Yo sé que soy (Bella) y (que) duermo, y sin embargo, (no) espero el (beso) ajeno (para) despertar.

miércoles, junio 07, 2006

celulas... no celulares...

2 New Efforts to Develop Stem Cell Line for Study
(del NYtimes)

Scientists at two universities — Harvard and the University of California, San Francisco — will try to develop embryonic stem cells from the adult cells of patients suffering from certain diseases.

Their purposes in creating the cell lines, which require making an early human embryo, are to study how the diseases develop and also to see if replacement cells can be generated to repair the patient's own degenerating tissues. But the field, despite its much emphasized promise, faces many serious uncertainties.

"Clinical applications may be a decade or more away," said George Q. Daley, a Harvard expert on blood diseases.

Harvard announced its plans yesterday at a news conference; the University of California, San Francisco, did so less conspicuously a month ago, resuming a program abandoned in 2001. Both universities, having received required approvals, will at first obtain the human eggs needed for cloning from fertility clinics, starting with eggs deemed too low quality to produce a successful pregnancy. Both programs are privately financed because federal support for human stem cell research is available only for cell lines made before August 9, 2001.

Advanced Cell Technology in Worcester, Mass., also has a human nuclear transfer program "well under way," said Robert Lanza, the company's vice president, but has run into problems in recruiting egg donors. Under guidelines issued by the National Academy of Sciences, which are voluntary but widely observed, donors may not be paid anything beyond expenses.

The new efforts, if successful, would accomplish what the disgraced South Korean scientist Woo-Suk Hwang claimed he had achieved in articles published in Science in 2004 and 2005. Both papers turned out to be based on forged data. But the flaws remained undetected by scientists involved in the cloning field, raising doubts about the rigor and expertise with which the new field was being conducted. The problems came to light not through criticism by scientific peers, but only after a whistle-blower in Dr. Hwang's lab contacted a Seoul television station.

The University of California, San Francisco, said last month that one of its researchers, Renee Reijo Pera, would start the cloning procedure, which involves transferring the nucleus of an adult cell into an unfertilized egg whose own nucleus has been removed.

A composite egg of this kind should develop in glassware into an early embryo, or blastocyst, from which embryonic stem cells could be isolated. There is no evident reason why this should not work in people as it has already done in several animal species, yet so far no one has succeeded. Dr. Hwang used no less than 2,000 fresh eggs donated by a healthy women but failed to accomplish anything useful.

Dr. Reijo Pera will switch to using donated eggs if those rejected by fertility clinics do not work, a university spokeswoman said. Harvard researchers said yesterday that they too would seek to derive eggs from healthy donors in the future.

Dr. Lanza, of Advanced Cell Technology, said that freshly harvested human eggs were "much better" for nuclear transfer experiments but that a six-month campaign by his company to recruit donors "appears to be a losing effort."

Many women had come forward, saying they would donate their eggs for research without compensation but, after seeing the battery of tests required, "most of the donors change their mind once they realize what's involved," Dr. Lanza said.

If research should establish that replacement tissues can be developed for a patient through the nuclear transfer technique, probably tens or hundreds of donated human eggs would be needed for each operation. Some scientists regard such a requirement as impractical, arguing that researchers should learn how to reprogram an adult cell's nucleus back to embryonic state without the use of human eggs. But this requires a far deeper understanding of human cells than is yet at hand.

Three Harvard scientists described their proposed research yesterday, promising not to discuss it further in public until they had firm results ready to be published. Dr. Daley hopes to develop, via nuclear transfer, embryonic stem cells from patients with blood diseases. He will try to correct the genetic defect behind the disease, then develop blood stem cells that could be engrafted in the patient's marrow.

The two other scientists, Douglas Melton and Kevin Eggan, said they would develop embryonic stem cell lines from diabetic patients, hoping to understand the development of the disease from its earliest moments at the cellular level.